As with the electronics and computer industries, trends in chemical and biochemical analysis are moving toward faster, smaller and less expensive systems and methods for performing all types of chemical and biochemical analyses.
The call for smaller systems and faster methods has been answered, in part, through the development of microfluidic technologies, which perform chemical and biochemical analyses and syntheses in extremely small-scale integrated fluid networks. For example, published International Patent Application No. WO 98/00231 describes microfluidic devices, systems and methods for performing a large number of screening assays within a single microfluidic device that is on the order of several square centimeters. Such developments have been made possible by the development of material transport systems that are capable of transporting and accurately dispensing extremely small volumes of fluid or other materials. See Published International Application No. 96/04547 to Ramsey.
By accurately controlling material transport among a number of integrated channels and chambers, one is able to perform a large number of different analytical and/or synthetic operations within a single integrated device. Further, because these devices are of such small scale, the amount of time for reactants to transport and/or mix, is very small. This results in a substantial increase in the throughput level of these microfluidic systems over the more conventional bench-top systems.
By reducing the size of these microfluidic systems, one not only gains advantages of speed, but also of cost. In particular, these small integrated devices are typically fabricated using readily available microfabrication technologies available from the electronics industries which are capable of producing large numbers of microfluidic devices from less raw materials. Despite these cost savings, it would nonetheless be desirable to further reduce the costs required to manufacture such microfluidic systems.
A number of reporters have described the manufacture of microfluidic devices using polymeric substrates. See, e.g., Published International Patent Application No. WO 98/00231 and U.S. Pat. No. 5,500,071. In theory, microfabrication using polymer substrates is less expensive due to the less expensive raw materials, and the `mass production` technologies available to polymer fabrication and the like.
However, despite these cost advantages, a number of problems exist with respect to the fabrication of microfluidic devices from polymeric materials. For example, because polymeric materials are generally flexible, a trait that is accentuated under certain fabrication methods, e.g., thermal bonding, solvent bonding and the like, it is difficult to accurately manufacture microscale structural elements in such polymeric materials. In particular, the microscale structures are easily deformed under manufacturing conditions, either due to applied pressures or relaxation of the polymer matrix based upon its intrinsic structural properties.
Accordingly, it would generally be desirable to have a method of fabricating microscale devices where the structural aspects of the device are not substantially perturbed during the fabrication process. The present invention meets these and other needs.